To limit a stroke of a piston installed in a power cylinder, some integral power steering apparatuses are equipped with a stroke limiter. One such stroke-limiter equipped integral power steering apparatus has been disclosed in Japanese Published Utility Model application No. 4-65667 (hereinafter is referred to as JU4-65667). In the stroke-limiter equipped integral power steering apparatus disclosed in JU4-65667, the stroke limiter is comprised of a plunger-equipped limiter valve. When a steering wheel angle (a steering wheel movement) reaches a predetermined value, in other words, when a sector gear reaches a predetermined angular position, the tip of the plunger is pushed by the tooth face of the sector gear and thus the stroke limiter (the limiter valve) becomes opened. With the stroke limiter kept at its valve-open position, an assisting pressure drops, and hence a piston stroke is suppressed or limited properly.